function _strtotime(unixtimestamp) {
    if(!unixtimestamp){
        return '';
    }
    var unixtimestamp = new Date(unixtimestamp * 1000);
    var year = 1900 + unixtimestamp.getYear();
    var month = "0" + (unixtimestamp.getMonth() + 1);
    var date = "0" + unixtimestamp.getDate();
    var hour = "0" + unixtimestamp.getHours();
    var minute = "0" + unixtimestamp.getMinutes();
    var second = "0" + unixtimestamp.getSeconds();
    return year + "-" + month.substring(month.length - 2, month.length) + "-" + date.substring(date.length - 2, date.length) + " " + hour.substring(hour.length - 2, hour.length) + ":" + minute.substring(minute.length - 2, minute.length) + ":" + second.substring(second.length - 2, second.length);
}